U.S. patent application number 15/199105 was filed with the patent office on 2018-01-04 for transducer reliability testing.
The applicant listed for this patent is Mellanox Technologies, Ltd.. Invention is credited to Lion Bassat, Alex Burlak, Morees Ghandour, Itshak Kalifa, Evelyn Landman, Kfir Margalit, Elad Mentovich, Sylvie Rockman, Alon Webman.
Application Number | 20180003762 15/199105 |
Document ID | / |
Family ID | 60807376 |
Filed Date | 2018-01-04 |
United States Patent
Application |
20180003762 |
Kind Code |
A1 |
Burlak; Alex ; et
al. |
January 4, 2018 |
TRANSDUCER RELIABILITY TESTING
Abstract
A transducer reliability testing and VCSEL failure prediction
method are provided. The method includes applying a testing
temperature and a constant current to a VCSEL for a testing time.
The method monitors a forward voltage of the VCSEL and determines
if a first change in forward voltage is above a first predetermined
threshold over the testing time and if a second change in forward
voltage is above a second predetermined threshold over a portion of
the testing time. The method determines failure of the VCSEL if
either of these predetermined thresholds are exceeded. The method
determines passage of the VCSEL if the first change in the forward
voltage and the second change in the forward voltage are both below
the first predetermined threshold and the second predetermined
threshold, respectively.
Inventors: |
Burlak; Alex; (Pardes Hana
Karkur, IL) ; Bassat; Lion; (Pardes Hana Karkur,
IL) ; Kalifa; Itshak; (Ramat Gan, IL) ;
Margalit; Kfir; (Rehovot, IL) ; Ghandour; Morees;
(Rama Village, IL) ; Webman; Alon; (Tel Aviv,
IL) ; Mentovich; Elad; (Tel Aviv, IL) ;
Rockman; Sylvie; (Zichron Yaakov, IL) ; Landman;
Evelyn; (Haifa, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mellanox Technologies, Ltd. |
Yokneam |
|
IL |
|
|
Family ID: |
60807376 |
Appl. No.: |
15/199105 |
Filed: |
June 30, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 31/2635 20130101;
H01S 5/0021 20130101; G01R 31/2874 20130101; G01R 31/2642 20130101;
H01S 5/0014 20130101; H01S 5/183 20130101 |
International
Class: |
G01R 31/26 20140101
G01R031/26; G01R 31/28 20060101 G01R031/28 |
Claims
1. A method for testing a vertical cavity surface emitting laser
(VCSEL) for emitting light, comprising: applying a testing
temperature to a VCSEL for a testing time; applying a constant
current to the VCSEL for the testing time; monitoring a forward
voltage for the VCSEL; determining, if a first change in the
forward voltage is above a first predetermined threshold over the
testing time, failure of the VCSEL; determining, if a second change
in the forward voltage is above a second predetermined threshold
over a portion of the testing time, failure of the VCSEL; and
determining, if the first change in the forward voltage over the
testing time is below the first predetermined threshold and if the
second change in the forward voltage over the portion of the
testing time is below the second predetermined threshold, passage
of the VCSEL.
2. The method according to claim 1, wherein the testing temperature
is about 150.degree. C.
3. The method according to claim 2, wherein the testing time is
about 464 hours.
4. The method according to claim 3, wherein the first predetermined
threshold is 10 mV.
5. The method according to claim 3, wherein the second
predetermined threshold is 20 mV.
6. The method according to claim 3, wherein the portion of the
testing time is a final 336 hours of the testing time.
7. The method according to claim 3, wherein the change in forward
voltage is determined at 8 hours, 128 hours, and 464 hours of the
testing time.
8. The method according to claim 1, wherein the testing temperature
is about 25.degree. C.
9. The method according to claim 1, further comprising subjecting
the VCSEL to a burn-in period, wherein the burn-in period is a
4-hour time period prior to the testing time in which the VCSEL is
subjected to a temperature of about 150.degree. C.
10. The method according to claim 1, wherein upon determining
failure of the VCSEL, one or more operating parameters of the VCSEL
are adjusted.
11. The method according to claim 1, wherein the forward voltage
for the VCSEL is measured at a driver of the VCSEL.
12. A non-transitory computer-readable medium having computer
program instructions stored thereon, the computer program
instructions being configured to: monitor an operating temperature
of a VCSEL; monitor an operating current of the VCSEL; monitor a
forward voltage for the VCSEL; determine, if a change in the
forward voltage is above a predetermined threshold over a period of
time, failure of the VCSEL; determine, if the change in the forward
voltage over the period of time is below the predetermined
threshold, passage of the VCSEL; and adjust, in an instance in
which failure of the VCSEL is determined, an operating parameter of
the VCSEL.
13. The computer-readable medium according to claim 12, wherein the
computer program instructions are embodied by firmware installed on
a micro-controller or a driver.
14. The computer-readable medium according to claim 12, wherein the
operating temperature is about 25.degree. C.
15. The computer-readable medium according to claim 14, wherein the
predetermined threshold is 20 mV
16. The computer-readable medium according to claim 14, wherein the
predetermined threshold is 10 mV.
17. The computer-readable medium according to claim 12, further
comprising subjecting the VCSEL to a burn-in period, wherein the
burn-in period is a 4-hour time period prior to installation in
which the VCSEL is subjected to a temperature of about 150.degree.
C.
18. The computer-readable medium according to claim 12, wherein the
operating parameter that is adjusted comprises the operating
temperature of the VCSEL.
19. The computer-readable medium according to claim 12, wherein the
operating parameter that is adjusted comprises the operating
current of the VCSEL.
20. The computer-readable medium according to claim 12, wherein the
computer program instructions are further configured to generate an
alarm condition in an instance in which failure of the VCSEL is
determined.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates generally to vertical-cavity
surface-emitting lasers (VCSELs) and, more particularly, to
apparatuses and associated methods of predicting the failure of
VCSELs.
BACKGROUND OF THE INVENTION
[0002] Optical communication systems include cables that transmit
signals over optical media. Optical communication systems may
include separate circuitry that facilitates the transmissions along
the optical cables using one or more transducers. For example,
modern optical communications systems may use vertical-cavity
surface-emitting lasers (VCSELs) as optoelectronic transducers that
convert electrical signals to light for transmission through the
fiber optic cables.
[0003] One of the primary modes of failure in optical communication
systems is the random failure of the optoelectronic transducers.
Traditionally, failure in these transducers (e.g., the VCSELs)
requires the entire optoelectronic transducer to be replaced, which
incurs substantial cost in terms of down time, labor, and other
costs to the user.
[0004] Applicant has identified a number of additional deficiencies
and problems associated with conventional VCSELs and associated
testing methods. Through applied effort, ingenuity, and innovation,
many of these identified problems have been solved by developing
solutions that are included in embodiments of the present
invention, many examples of which are described in detail
herein.
BRIEF SUMMARY OF THE INVENTION
[0005] Accordingly, the methods described herein provide improved
mechanisms for detecting potential failures in optoelectronic
components, such as VCSELs, during a testing phase (prior to
installation and operation of the component in an optical
communication system), and further provide improved mechanisms for
monitoring optoelectronic components (e.g., VCSELs) during
operation and compensating for changes in the operational
characteristics of the components over time by adjusting relevant
operating parameters to maintain desired results.
[0006] In some embodiments, a method for testing a vertical cavity
surface emitting laser (VCSEL) for emitting light is provided,
where the method comprises applying a testing temperature to a
VCSEL for a testing time; applying a constant current to the VCSEL
for the testing time; and monitoring a forward voltage for the
VCSEL. If a first change in the forward voltage is above a first
predetermined threshold over the testing time, failure of the VCSEL
is determined. In addition, if a second change in the forward
voltage is above a second predetermined threshold over a portion of
the testing time, failure of the VCSEL is determined. Thus, if the
first change in the forward voltage over the testing time is below
the first predetermined threshold and if the second change in the
forward voltage over the portion of the testing time is below the
second predetermined threshold, passage of the VCSEL is
determined.
[0007] In some cases, the testing temperature may be about
150.degree. C., and the testing time may be about 464 hours. In
such cases, the first predetermined threshold may be 10 mV, and the
second predetermined threshold may be 20 mV. The portion of the
testing time may, in some cases, be a final 336 hours of the
testing time. Moreover, the change in forward voltage may be
determined at 8 hours, 128 hours, and 464 hours of the testing
time.
[0008] In other cases, the testing temperature may be about
25.degree. C.
[0009] The VCSEL may, in some embodiments, be subjected to a
burn-in period, wherein the burn-in period is a 4-hour time period
prior to the testing time in which the VCSEL is subjected to a
temperature of about 150.degree. C.
[0010] In still other cases, upon determining failure of the VCSEL,
one or more operating parameters of the VCSEL may be adjusted.
Furthermore, the forward voltage for the VCSEL may be measured at a
driver of the VCSEL.
[0011] In other embodiments, a non-transitory computer-readable
medium is provided having computer program instructions stored
thereon, the computer program instructions being configured to
monitor an operating temperature of a VCSEL; monitor an operating
current of the VCSEL; and monitor a forward voltage for the VCSEL.
The computer program instructions may further be configured to
determine failure of the VCSEL, if a change in the forward voltage
is above a predetermined threshold over a period of time; to
determine passage of the VCSEL if the change in the forward voltage
over the period of time is below the predetermined threshold, and
to adjust an operating parameter of the VCSEL in an instance in
which failure of the VCSEL is determined.
[0012] In some cases, the computer program instructions may be
embodied by firmware installed on a micro-controller or a driver.
The operating temperature may be about 25.degree. C. The
predetermined threshold may, in some cases, be 20 mV, while in
other cases the predetermined threshold may be 10 mV.
[0013] Additionally, the VCSEL may, in some cases, be subjected to
a burn-in period, wherein the burn-in period is a 4-hour time
period prior to installation in which the VCSEL is subjected to a
temperature of about 150.degree. C. Moreover, the operating
parameter that is adjusted may comprise the operating temperature
of the VCSEL, while in other cases the operating parameter that is
adjusted may comprise the operating current of the VCSEL.
[0014] In some embodiments, the computer program instructions may
be further configured to generate an alarm condition in an instance
in which failure of the VCSEL is determined.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0015] Having thus described the invention in general terms,
reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:
[0016] FIG. 1a shows a block diagram illustrating testing
procedures, in accordance with some embodiments discussed
herein;
[0017] FIG. 1b shows a diagram illustrating the testing time, in
accordance with some embodiments discussed herein;
[0018] FIG. 2 shows a block diagram schematically illustrating an
optical transceiver system, in accordance with some embodiments
discussed herein; and
[0019] FIG. 3 shows a block diagram illustrating monitoring
procedures having a warning or adjustment feature, in accordance
with some embodiments discussed herein.
DETAILED DESCRIPTION
Overview
[0020] Optical cables are comprised of optical fibers. Optical
cables may be utilized in conjunction with optical transmitters and
receivers built into transceiver modules and systems located at the
ends of the optical cables for transmitting and receiving the
optical communication signals carried by the fibers. The
transceiver modules may include small form-factor pluggable (SFP)
transceivers or dual SFP transceivers. The transceiver modules or
systems may plug into suitable electrical communication ports, such
as Gigabit Ethernet or InfiniBand.RTM. ports, of switching and
computing equipment. Optoelectronic components in the transceiver
modules and systems may convert the high-speed electrical signals
output by the ports into optical signals for transmission over the
fibers. In addition, the optoelectronic components may convert the
optical signals received over the fibers into high-speed electrical
signals for input to the electrical communication ports.
[0021] In many transceiver modules and systems, laser diodes, such
as VCSELs, are used to generate optical signals for transmission
over optical fibers. VCSELs in particular are favored for their
high bandwidth and efficiency. In some implementations, an array of
such VCSELs is used to drive a corresponding array of optical
fibers, which are joined together in a ribbon configuration.
Optical fibers may be connected to both VCSELs and photodiode
configurations on opposing ends such that one or more photodiodes
may receive the light from the VCSELs at a receiving end of the
fibers and convert the incident light into electrical signals. One
or more sources may provide the electrical signals for transmission
from a transmitting device or may receive the electrical signals
after receipt from the transmitting device, and the sources may
provide the electrical signals to the VCSELs for transmission as
optical signals via optical fibers or may receive the electrical
signals from the photodiodes via optical fibers.
[0022] In manufacturing transceiver modules and systems, laser
diodes, such as VCSELs, are often subjected to a high-temperature
operating life (HTOL) testing procedure. An HTOL test is a test for
determining the reliability of the components found in the
transceiver modules and systems, and may be conducted prior to
installation of the component in an operational system.
Conventional HTOL tests subject a VCSEL to an elevated temperature
for a period of time and determine the expected reliability of the
VCSEL once it is installed in an optical communication system in a
datacenter based upon the observed results. Often, the VCSEL may be
subjected to a burn-in period before the HTOL test is conducted to
ensure that the VCSEL has achieved uniform characteristics in order
to improve testing results. Conventional HTOL testing procedures,
however, may fail to accurately identify VCSELs that have a high
likelihood of failure or are prone to certain modes of failure
(e.g., random failures). For example, the tolerances used in
conventional HTOL testing procedures are often broad, such that
VCSELs exhibiting characteristics associated with the random
failure of the VCSEL are deemed to pass the testing and are
provided to users for installation, resulting in their eventual
premature failure in operation.
[0023] Embodiments of the present invention that are described
hereinbelow provide an improved method for testing the reliability
and accurately predicting the failure of a VCSEL prior to
installation of the VCSEL in an operational optical communication
system. In addition, embodiments of the present invention also
provide for continual monitoring of the VCSEL during operation,
once installed in the system, to detect and/or compensate for
changes in the operational characteristics leading up to failure of
the component.
[0024] As described in greater detail below, the method may be
implemented by a programmable optoelectronic interface that
subjects the VCSEL to a temperature for a period of time (e.g., a
testing time) in order to test the reliability of the VCSEL. The
interface may subject the VCSEL to a constant current during the
testing time in order to monitor the forward voltage change
experienced by the VCSEL. The forward voltage is the voltage drop
across the VCSEL, such as the difference between the voltage at an
anode of the VCSEL and the voltage at a cathode of the VCSEL, as
would be understood by one or ordinary skill in the art in light of
this disclosure. The change in forward voltage may be determined at
various intervals during the testing time. The method may compare
the change in forward voltage experienced by the VCSEL with various
predetermined thresholds at different time periods, as described
below. The method may predict the failure of the VCSEL if any of
the predetermined threshold values are exceeded. Thus, through
applied effort, ingenuity, and innovation, the inventors have found
that a change in forward voltage experienced by the VCSEL can be
correlated to defects that influence the VCSEL performance. If the
predetermined threshold values are not exceeded during the testing
time, the method may quantify the reliability of the VCSEL.
[0025] In some embodiments, a method may be executed while the
VCSEL is in operation to predict and/or prevent or compensate for
the failure of the VCSEL. In some embodiments, the method may, upon
determining that the change in forward voltage has exceeded a
threshold value, present a warning to the user such that the user
may prepare for the failure of the VCSEL. The method may be
implemented by a programmable optoelectronic interface comprised of
a controller (e.g., a microcontroller) and a driver, as described
below. In such an embodiment, the controller and the driver may be
configured to provide the warning to the user. Additionally, the
controller and the driver, upon determining that the change in
forward voltage has exceeded a threshold value, may be configured
to adjust an operating parameter of the VCSEL to increase the
amount of time the VCSEL is operational before failure and/or
compensate for changes in the operating characteristics of the
VCSEL.
[0026] In some embodiments, the method may be enacted via an
optical transceiver system comprised of a VCSEL, a driver, and/or a
micro-controller. The driver and/or micro-controller may operate to
ensure that the testing/monitored conditions (e.g., the
temperature, current, etc.) are constant and accurate throughout
the process. The driver and/or micro-controller may also operate to
monitor the forward voltage experienced by the VCSEL and determined
a value for this forward voltage over a period of time. The driver
and/or micro-controller may compare this determined forward voltage
value with one or more predetermined threshold values and
predict/compensate for the likelihood of failure of the VCSEL, as
described below in greater detail.
[0027] For the sake of clarity and convenience of description, the
embodiments that are described below refer to a particular optical
cable configuration, using VCSELs as emitters and certain types of
switching elements. The principles of the present invention,
however, may similarly be implemented using other types of emitters
(e.g., other types of lasers), modulators, and switching elements,
as well as other optoelectronic transceiver components (e.g.,
photodiodes and differently configured optical cables and connector
modules).
VCSEL Testing
[0028] With reference to FIG. 1a, a block diagram is provided that
illustrates a VCSEL failure prediction method 100 for use with some
embodiments described herein. The method may include the steps of
applying a testing temperature at Block 105 and a constant current
at Block 110 to a VCSEL for a testing time (e.g., a period of time
over which the test is conducted), such as prior to installation of
the VCSEL in an optical communication system. The method may also
include monitoring the forward voltage of the VCSEL at Block 115
and determining the forward voltage change at the end of the
testing time at Block 125 and/or after a portion of the testing
time at Block 120 has passed. The method may utilize predetermined
thresholds (e.g., at Blocks 130, 135) to predict the failure of the
VCSEL at Block 140 or the passage of the VCSEL at Block 145.
[0029] With continued reference to FIG. 1a, a VCSEL failure
prediction method 100 may apply a testing temperature to the VCSEL
for a testing time at Block 105. In some embodiments, the VCSEL may
be tested at a nominal temperature of 150.degree. C. In some
embodiments, the VCSEL may be tested at a nominal temperature of
25.degree. C. The use of two or more temperatures during testing
may, in some cases, provide more accurate results. For example, an
elevated testing temperature (e.g., a nominal temperature of
150.degree. C.) may be used in some cases to accelerate the
different failure mechanisms applicable to the component being
tested (e.g., the VCSEL). Moreover, other temperatures may be used
to test the reliability of other types of components. The testing
temperatures may, for example, be determined empirically and may
change depending on the component being tested. In some
embodiments, the testing temperature may be selected using the
Arrhenius equation (for reliability), an equation used to calculate
thermal acceleration factors for semiconductor device
time-to-failure distributions.
[0030] The VCSEL failure prediction method 100 may be employed by a
testing system, such as at the manufacturer site, to determine
whether the VCSEL can be installed in a transceiver system (e.g.,
an optical transceiver system 200 shown in FIG. 2). In some
embodiments, for example, the testing time may be a nominal period
of 464 hours.
[0031] In addition to an elevated temperature, the VCSEL failure
prediction method 100 may also apply a constant current to the
VSCEL at Block 110, such that the forward voltage of the VCSEL may
be monitored at Block 115. In particular, Ohms law states that
V=IR, where V is voltage, I is current, and R is resistance, which
is a characteristic of the VCSEL. By utilizing a VCSEL with a
particular resistance value and applying a constant current at
Block 110, a monitored change in the voltage of the VCSEL may be
indicative of a change in the characteristics of the VCSEL, namely,
a change in the VCSEL's resistance. This change in voltage may thus
be indicative of the likelihood of failure of the VCSEL, as a
change in the VCSEL's operating characteristics may indicate or
predict a change in the operation of the VCSEL, which in many cases
may be regarded as a failure of the component.
[0032] The VCSEL failure prediction method 100 may utilize a first
predetermined threshold and a second predetermined threshold with
respect to a forward voltage change determined at the end of the
testing time and/or over a portion of the testing time,
respectively, as shown in Blocks 120, 125. In some embodiments, for
example, the VCSEL failure method 100 may determine the forward
voltage change over a portion of the testing time at Block 120,
where the portion of the testing time is the final 336 hours of the
testing time. For example, if the testing time (e.g., the duration
of the test) is 400 hours, the portion of the testing time that may
be monitored in this case may be from Hour 64 to Hour 400 (e.g.,
the final 336 hours of the test). In such an embodiment, the method
may, for example, determine if the change in the forward voltage
exceeds a second predetermined threshold value of 10 mV at any time
during that portion (e.g., the final 336 hours of the testing
time). If the method determines that the change in forward voltage
over the portion of the testing time exceeds the second
predetermined threshold at Block 130, the method may determine that
the VCSEL has a high likelihood of failure at Block 140.
[0033] Additionally or alternatively, in some embodiments, the
VCSEL failure prediction method 100 may determine the forward
voltage change over the entire testing time at Block 125, and in
some cases the entire testing time may be a nominal period of 464
hours. In such an embodiment, the method may, for example,
determine if the change in the forward voltage exceeds a first
predetermined threshold value of 20 mV. If the method determines
that the change in forward voltage over the entirety of the testing
time at Block 125 exceeds the first predetermined threshold at
Block 135, the method may determine that the VCSEL has a high
likelihood of failure at Block 140.
[0034] In some embodiments, the VCSEL failure prediction method 100
may determine the passage of the VCSEL at Block 145 if the change
in the forward voltage is determined over a portion of the testing
time at Block 120 is below the second predetermined threshold and
also if the change in the forward voltage is determined at the end
of the testing time at Block 125 is below the first predetermined
threshold at Blocks 130, 135, respectively. In such an embodiment,
the VCSEL failure prediction method 100 may quantify the
reliability of the VCSEL.
[0035] Although the VCSEL failure prediction method 100 in FIG. 1a
is described as determining the forward voltage of the VCSEL at the
end of the testing time 125 and over a portion of the testing time
120, the present disclosure contemplates that the forward voltage
change of the VCSEL may be determined at any point throughout the
testing time. By way of example, the VCSEL failure prediction
method 100 may determine the change in forward voltage at the
8.sup.th hour, at the 128.sup.th hour, at the 464.sup.th hour,
etc.
[0036] In some embodiments, the VCSEL failure prediction method 100
may employ a burn-in period at Block 150 prior to applying the
testing temperature to the VCSEL for a testing time at Block 105.
Burn-in periods may be utilized in transceiver systems and other
optical communication systems, for example, as a means for
normalizing the transceiver components prior to testing. During a
burn-in period at Block 150, the VCSEL may be subjected to an
elevated temperature for a period of time to eliminate the
likelihood of potential spikes in forward voltage change to ensure
accurate results during the testing of the VCSEL failure prediction
method 100. For example, in some embodiments, the burn-in period
may be a 4-hour time period in which the VCSEL is subjected to a
nominal temperature of 150.degree. C.
[0037] With reference to FIG. 1b, for example, an example timeline
is illustrated that shows a burn-in period 155, a testing time 150,
and a portion of the testing time 160. As described in detail
above, in some embodiments, the method may, for example, employ a
burn-in period 155 of 4 hours, a testing time 150 of 464 hours, and
a portion of the testing time 160 being the final 336 hours of the
testing time 150.
[0038] The present disclosure contemplates that it may be
advantageous to the user for the operating parameters of the VCSEL
to be monitored during operation of the VCSEL as part of an optical
communication system (e.g., in the installed configuration) by
determining a change in the forward voltage of the VCSEL. In such
an embodiment, a method may, for example, monitor an operating
temperature and an operating current (e.g., inputted electrical
signal) of the VCSEL. In this way, the forward voltage may be
determined by the method, and a change in the determined forward
voltage may be compared with one or more predetermined threshold
values to predict the likelihood of failure of the VCSEL, as
described herein in greater detail. Upon predicting the likelihood
of failure of the VCSEL, the method may provide a warning to the
user and/or may adjust one or more operating parameters of the
VCSEL to increase the amount of time the VCSEL is operational
before failure and/or compensate for changes in the operating
characteristics of the VCSEL.
[0039] With reference to FIG. 3, for example, a block diagram is
provided that illustrates a VCSEL failure prediction method 300 for
use with some embodiments described herein. The method may include
the steps of monitoring an operating temperature at Block 305 and
monitoring an operating current at Block 310 of a VCSEL during
operation (e.g., with the VCSEL installed in the optical
communication system). The method may also include monitoring the
forward voltage of the VCSEL at Block 315 and determining a forward
voltage change over a period of time during operation of the VCSEL
at Block 320. The method may utilize a predetermined threshold to
predict the failure of the VCSEL by determining whether the change
in the forward voltage (over the time of operation) is above the
predetermined threshold at Block 325 and may further provide a
warning to the user at Block 330 in the event the change in forward
voltage is not in conformance. In some cases, the method may, upon
determining that the forward voltage change exceeds the
predetermined threshold at Block 325, adjust the operation of the
VCSEL to compensate for the forward voltage change at Block 335,
such as by providing higher or lower current as the electrical
input signal to the VCSEL and/or adjusting an operating temperature
of the VCSEL. Accordingly, in such embodiments, the method may be
conducted continuously during operation of the VCSEL, with alerts
provided to the user. In still other cases, the forward voltage
change data may be stored and/or analyzed to determine trends, even
when the forward voltage change is below the predetermined
threshold (e.g., in conformance).
[0040] With continued reference to FIG. 3, a VCSEL failure
prediction method 300 may monitor an operating temperature of the
VCSEL at Block 305. In some cases, for example, the operating
temperature may be a nominal temperature of 25.degree. C. The VCSEL
failure prediction method 300 may also monitor an operating current
of the VSCEL at Block 310 such that the forward voltage of the
VCSEL may be monitored at Block 315.
[0041] The VCSEL failure prediction method 300 may refer to a
predetermined threshold 325 and may use the predetermined threshold
to determine whether the monitored forward voltage is acceptable
over a period of time that the VCSEL is in operation at Block 320.
If the method determines that the change in forward voltage over
that period of time exceeds a predetermined threshold at Block 325,
the method may provide a warning to the user at Block 330. In some
embodiments, if the predetermined threshold value is not exceeded
at Block 325, the method may continue operating the VCSEL as before
(e.g., without changes to the operational parameters) and may
continue monitoring the VCSEL at Block 340, such as by continuing
to monitor an operating temperature, an operating current, and a
forward voltage with respect to the predetermined threshold.
[0042] In some embodiments, the VCSEL failure prediction method 300
may, upon determining that the predetermined threshold 325 has been
exceeded, adjust the operating parameters of the VCSEL 210 so as to
compensate for the change in forward voltage at Block 355. For
example, the inputted electrical signal to the VCSEL 210 may be
adjusted up or down to produce a desired optical signal (e.g., an
optical signal that is at the desired wavelength or an acceptable
range of wavelengths) from the VCSEL under the modified operating
conditions detected by the method. In such an embodiment, this
compensation for the change in forward voltage 355 may serve to
prolong the amount of time the VCSEL is operational (e.g.,
producing the desired optical signals) before failure.
[0043] Although the VCSEL failure prediction method 300 in FIG. 3
is described as determining the forward voltage of the VCSEL over a
period of time at Block 320, the present disclosure contemplates
that the forward voltage change of the VCSEL may be determined at
any point throughout the period of time that it is being monitored.
By way of example, the VCSEL failure prediction method 300 may
determine the change in forward voltage at the 8.sup.th hour, at
the 128.sup.th hour, and/or at the 464.sup.th hour of the operation
time, or at regular intervals thereof. As described above, in some
embodiments, the VCSEL failure prediction method 300 may employ a
burn-in period at Block 345 prior to installing and operating the
VCSEL 210.
[0044] The present disclosure contemplates that the VCSEL failure
prediction method 300 may be implemented in an optical transceiver
system (e.g., the optical transceiver system 200 in FIG. 2) via a
driver and/or micro-controller (e.g., the driver 205 and the
microcontroller 215 in FIG. 2) during operation (e.g., after the
optical transceiver system 200 has been installed in an optical
communication system in a datacenter and is in operation). In such
an embodiment, the driver and/or micro-controller may continuously
or continually monitor the forward voltage change of the VCSEL
during operation and may continuously/continually compare the
determined forward voltage to the predetermined threshold,
according to embodiments of the method 300 described above. In such
an embodiment, the VCSEL failure prediction method 300 may provide
a warning to the user at Block 330, such that the user may prepare
for the failure of the VCSEL and respond accordingly. Additionally,
as described above, in some embodiments the method 300 may provide
for the automatic adjustment of the operating parameters of the
VCSEL at Block 335, such as by communicating with the driver 205
and/or the micro-controller 215, and adjusting the operating
parameters of the VCSEL (e.g., the operating temperature and/or
current) to compensate for the changes in the output of the VCSEL
that would otherwise be caused by the changes in the VCSEL's
operating characteristics, thereby prolonging the amount of time
the VCSEL is operational.
[0045] With reference to FIG. 2, for example, a block diagram is
provided that shows schematically an optical transceiver system 200
capable of employing embodiments of the VCSEL failure prediction
method 100 and/or the (installed) failure prediction method 300
shown in FIGS. 1 and 3, respectively. An optical transceiver system
200 may include a driver 205, a VCSEL 210, and/or a
micro-controller 215. In some cases, the method 300 may be
implemented via firmware installed in the driver 205 and/or the
micro-controller 215. For example, the driver 205 and/or the
micro-controller 215 may include non-transitory computer-readable
medium having computer instructions stored thereon. The driver 205
may be configured to provide an electrical input (e.g., a current)
to the VCSEL 210 to produce an optical signal output from the VCSEL
at a desired wavelength. The driver 205 may be embodied as
hardware, software, and/or firmware, which may, in some cases,
include the functionality of the micro-controller 215. In other
cases, however, a separate micro-controller 215 may be provided
that is in communication with the driver 205 and directs the
operation of the driver, as shown in FIG. 2.
[0046] In some cases, the micro-controller 215 may be configured to
direct the driver 205 to apply a current to the VCSEL 210, such
that the forward voltage drop experienced by the VCSEL 210 may be
measured at the driver 205 by the micro-controller 215. The
micro-controller 215 may be configured, with regard to the
pre-installation method 100, to ensure that the testing conditions
(e.g., the testing temperature and the constant current values)
remain constant for the duration of the testing time. The
micro-controller may also be configured, with regard to method 300,
to monitor the operating parameters (e.g., the operating
temperature and the operating current) of the optical transceiver
system 200 to ensure accurate determinations of the forward voltage
drop experienced by the VCSEL 210, as measured at the driver
205.
[0047] Accordingly, as described above, FIGS. 1 and 3 illustrate
flowcharts of systems, methods, and computer program products
according to example embodiments of the invention. It will be
understood that each block of the flowcharts, and combinations of
blocks in the flowcharts, may be implemented by various means, such
as hardware, firmware, processor, circuitry, and/or other devices
associated with execution of software including one or more
computer program instructions, as described above. For example, one
or more of the procedures described above may be embodied by
computer program instructions. In this regard, the computer program
instructions which embody the procedures described above may be
stored by a memory employing an example embodiment of the present
invention and executed by a processor (e.g., the micro-controller
or driver with controller circuitry, or a computer implementing
testing prior to installation of the VCSEL or other component in an
optical communication system). As will be appreciated, any such
computer program instructions may be loaded onto a computer or
other programmable apparatus (e.g., hardware) to produce a machine,
such that the resulting computer or other programmable apparatus
implements the functions specified in the flowchart block(s). These
computer program instructions may also be stored in a
computer-readable memory that may direct a computer or other
programmable apparatus to function in a particular manner, such
that the instructions which execute on the computer or other
programmable apparatus provide operations for implementing the
functions specified in the flowchart block(s).
[0048] Many modifications and other embodiments of the inventions
set forth herein will come to mind to one skilled in the art to
which these inventions pertain having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. Although the figures only show certain components of the
methods and systems described herein, it is understood that various
other components may also be part of the optoelectronic coupler and
transceiver modules. In addition, the methods described above may
include fewer steps in some cases, while in other cases may include
additional steps. Modifications to the steps of the testing and
monitoring methods described above, in some cases, may be performed
in any order and in any combination.
[0049] Therefore, it is to be understood that the inventions are
not to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
* * * * *